mlx4: do not fire tasklet unless necessary
All rx and rx netdev interrupts are handled by respectively
by mlx4_en_rx_irq() and mlx4_en_tx_irq() which simply schedule a NAPI.
But mlx4_eq_int() also fires a tasklet to service all items that were
queued via mlx4_add_cq_to_tasklet(), but this handler was not called
unless user cqe was handled.
This is very confusing, as "mpstat -I SCPU ..." show huge number of
tasklet invocations.
This patch saves this overhead, by carefully firing the tasklet directly
from mlx4_add_cq_to_tasklet(), removing four atomic operations per IRQ.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index 6b86353..fa6d235 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
@@ -81,8 +81,9 @@ void mlx4_cq_tasklet_cb(unsigned long data)
static void mlx4_add_cq_to_tasklet(struct mlx4_cq *cq)
{
- unsigned long flags;
struct mlx4_eq_tasklet *tasklet_ctx = cq->tasklet_ctx.priv;
+ unsigned long flags;
+ bool kick;
spin_lock_irqsave(&tasklet_ctx->lock, flags);
/* When migrating CQs between EQs will be implemented, please note
@@ -92,7 +93,10 @@ static void mlx4_add_cq_to_tasklet(struct mlx4_cq *cq)
*/
if (list_empty_careful(&cq->tasklet_ctx.list)) {
atomic_inc(&cq->refcount);
+ kick = list_empty(&tasklet_ctx->list);
list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list);
+ if (kick)
+ tasklet_schedule(&tasklet_ctx->task);
}
spin_unlock_irqrestore(&tasklet_ctx->lock, flags);
}
diff --git a/drivers/net/ethernet/mellanox/mlx4/eq.c b/drivers/net/ethernet/mellanox/mlx4/eq.c
index 0509996..39232b6 100644
--- a/drivers/net/ethernet/mellanox/mlx4/eq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/eq.c
@@ -494,7 +494,7 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
{
struct mlx4_priv *priv = mlx4_priv(dev);
struct mlx4_eqe *eqe;
- int cqn = -1;
+ int cqn;
int eqes_found = 0;
int set_ci = 0;
int port;
@@ -840,13 +840,6 @@ static int mlx4_eq_int(struct mlx4_dev *dev, struct mlx4_eq *eq)
eq_set_ci(eq, 1);
- /* cqn is 24bit wide but is initialized such that its higher bits
- * are ones too. Thus, if we got any event, cqn's high bits should be off
- * and we need to schedule the tasklet.
- */
- if (!(cqn & ~0xffffff))
- tasklet_schedule(&eq->tasklet_ctx.task);
-
return eqes_found;
}